1. Technical Field
The present invention relates to a semiconductor device, and in particular relates to a semiconductor device configured to have a junction between an electrode pad of a semiconductor chip and a coupling member of a bonding wire or the like, encapsulated with an encapsulating resin.
2. Related Art
Japanese Patent Laid-Open No. S64-37,044 (1989) and Japanese Patent Laid-Open No. 1101-187,832 (1989) disclose typical semiconductor devices, which are manufactured by coupling electrode pads disposed on semiconductor chips to lead frames via coupling members such as wire bonding, and then are encapsulated with encapsulating resins.
In the semiconductor device described in Japanese Patent Laid-Open No. S64-37,044, gold (Au) wires are bonded to interconnects composed of aluminum (Al) silicon (Si) alloy.
Further, Japanese Patent Laid-Open No. S64-37,044 also discloses that a peeling-off is caused in a junction of a gold wire and an aluminum electrode pad when a plastic molded semiconductor device is kept in a higher temperature environment of 200 degree C. or higher, leading to a defective coupling, and that a similar phenomenon is also caused in a junction of a copper (Cu) wire and an aluminum electrode, in addition to the junction of the gold wire.
Further, Japanese Patent Laid-Open No. S64-37,044 additionally discloses that such phenomenon is related to level of free halogen generated in the encapsulating resin due to a thermal deterioration, and that such phenomenon can be improved by purifying a brominated epoxy resin employed as a fire retardant agent to reduce free bromine compounds generated due to a thermal decomposition.
Japanese Patent Laid-Open No. H01-187,832 discloses a bonding technology with Cu wires. Japanese Patent Laid-Open No. H01-187,832 describes that Cu is added to an electrode pad containing Al as a major constituent at relatively high ratio, for the purpose of providing an increased hardness of the electrode pad. More specifically, Cu is added to an electrode pad containing Al as a major constituent at a ratio of 2 to 12% to obtain hardness thereof at a level of 70 to 100 Vickers hardness. Japanese Patent Laid-Open No. H01-187,832 also describes that, since the hardness of such electrode pad is higher than that of the Al pad, a compressively bonded section is not peeled off during a process for bonding the Cu wire, and an impact applied to the lower layer of the electrode pad is reduced, so that damages such as cracks in the insulating film are avoided.